Direct Electrodeposition to Fabricate 3D Graphene Network Modified Glassy Carbon Electrode for Sensitive Determination of Tadalafil

Changzheng Xin,ShanShan Gao,Yaxin Din,Yanju Wu,Fei Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.1

In this work, pulse potential method (PPM) was presented to fabricate directly three-dimensional graphene (3DG) network on the surface of glassy carbon electrode (GCE). The morphological characteristic of 3DG network were investigated by means of Raman spectra, scanning electron microscopy (SEM) and electrochemical experiments. The 3DG network as a new voltammetric material was used to develop a high-sensitive electrochemical sensor for determination of tadalafil. Electrochemical tests showed that the 3DG network can help to enhance response due to the large accessible surface area as well as its excellent conductivity. Under the optimum conditions, the electrochemical response showed a linear relationship with tadalafil concentrations in the range of 5.0 x 10 -8 – 2.5 x 10 -5 mol L -1, and a low detection limit of 1.0 x 10 -8 mol L -1 was achieved for tadalafil. Moreover, the fabricated electrochemical sensor exhibited excellent selectivity, stability, reproducibility and repeatability, which make it very suitable for analytical applications for the trace level determination of tadalafil.

The International Financial Crisis and China: Impacts, Challenges, and Policies

Changzheng Dai,Xuan Qiao 서울대학교행정대학원 2010 Journal of Policy Studies Vol.25 No.1

The Chinese economy has been severely affected by the global financial crisis triggered by the United States. China’s imports and exports have been shrinking, and many enterprises closely related to international trade have been shut down. China has also been embarrassed by its US$2.1 trillion foreign exchange reserve and anxious to know how to manage it effectively. As the economic situation has become increasingly gloomy and uncertain, social problems such as layoffs have increased, and social security and social stability have inevitably appeared to worsen. This has caught the attention of the authorities. Public policies have to be adjusted and new policies established, and effective countermeasures have to be planned, so as to enable China to survive the crisis. Fiscal, monetary, industrial, and social policies have been initiated and are expected to work. Though their success is difficult to estimate, those measures nevertheless have manifested the determination of the Chinese government to conquer the current difficulties, as it has promised the people.

Mirror symmetry for exceptional unimodular singularities

Li, Changzheng,Li, Si,Saito, Kyoji,Shen, Yefeng European Mathematical Society Publishing House 2017 Journal of the European Mathematical Society Vol.19 No.4

Initial fault diagnosis of bearing based on AVMD-SE and multiscale enhanced morphological top-hat filter

Tong Wang,Changzheng Chen,Yuanqing Luo,Siyu Zhao,Shaohui Huang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

Early fault signature detection and background noise removal are essential for bearing fault diagnosis. A novel multiscale enhanced morphological top-hat filter fault diagnosis method, adaptive variational mode decomposition-sample entropy-multiscale enhanced top-hat filter (AVMD-SE-MEMTF), is proposed based on AVMD-SE noise reduction. First, gray wolf optimization algorithm is proposed to optimize the VMD to achieve the optimal decomposition parameters adaptively and combine with SE to eliminate the high noise components and improve the noise reduction effect. Then, based on the pulse extraction property of morphological operations, the concept of MEMTF is proposed. To enhance the multiscale index selection strategy, a synthesis method of eigenfrequency envelope coefficients is constructed to increase the accuracy of the operator during the vibration signal process. Finally, experimental and engineering results show that the proposed method has good diagnostic performance for weak faults in the presence of noise interference.

Acoustic signal analysis for gear fault diagnosis using a uniform circular microphone array

Chi Li,Changzheng Chen,Xiaojiao Gu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11

In this paper, a far-field acoustic signal processing method based on a uniform circular microphone array is proposed for the gear fault detection. The method takes ensemble empirical mode decomposition (EEMD) as a preprocessing approach, and the estimation of signal parameters via rotational invariance techniques (ESPRIT) is applied as the beamformer, which offers an adaptive and convenient approach to solve the serious aliasing and distortion in acoustic signals. The method greatly reduces the inherent demands for the microphone numbers and the computational load while holding a satisfying accuracy, making it more promising in practical engineering applications. Besides, aiming at the situation that gear failures cannot be judged solely by gear meshing frequencies (GMF) and sound source locations, seventeen statistical feature parameters are applied to the processed signals for the fault severity recognition, and six of them are found efficient, which provides a further reference for acoustic gear diagnosis.

Adaptive parameter-matching method of SR algorithm for fault diagnosis of wind turbine bearing

Xiaojiao Gu,Changzheng Chen 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3

The fault diagnosis of wind turbine bearings is challenging because of the heavy background noise and changes in wind speed. Stochastic resonance (SR) is an effective method of detecting fault signal from noise. However, the benefit of SR is seriously limited by the system parameters and the frequency of the input signal. A novel fault diagnosis method for wind turbine bearings, combining an adaptive SR algorithm that is based on quantum particle swarm optimization (QPSO) and frequency conversion based on frequency information exchange (FIE), is proposed. First, the frequency information of the fault characteristic signal is exchanged with the reference frequency by FIE, which can eliminate the limitation of the frequency band. Then, the SR system parameters are optimized by QPSO to avoid blind parameter selection. The signal after FIE is processed by the optimized SR system. The results of case study show that under the same input signal, the proposed method can achieve better signal-to-noise ratio and response amplitude than can the traditional double-side band modulation method and an SR method that is combined only with an optimization algorithm.

Influence of Spoke Parameters on Load Capacity of Non-Pneumatic Tires Using Orthogonal Study and Analysis of Variance

Weidong Liu,Changzheng Li,Qiushi Zhang 한국자동차공학회 2024 International journal of automotive technology Vol.25 No.2

This study aims to investigate the relationship between the static characteristics of non-pneumatic tires (NPTs) and spokedesign parameters using the fi nite element (FE) method. A three-dimensional FE model of the NPT was established. Theinfl uence of diff erent ranges of stress and strain on the calculation accuracy of the Neo-Hookean and Yeoh constitutivemodels was analyzed. Subsequently, the main design parameters—spoke thickness, spoke number, and arc curvature—wereselected according to the geometric characteristics of the spokes. The eff ects of these three parameters on the vertical stiff -ness, maximum spoke stress, overall maximum stress, and maximum and average contact pressures were examined usingunivariate and multivariate analysis methods. The range and variance analysis results indicated that the spoke thickness,spoke number, and arc curvature had a signifi cant eff ect on the vertical stiff ness. Finally, the relationship between the verticalstiff ness and product of the spoke thickness and number was obtained using a nonlinear fi tting method. When the arc curvatureof the spoke was less than 5 m −1 , the errors between the calculated and simulated vertical stiff ness did not exceed 5%. This observation can be used to facilitate the rapid design of spoke parameters under diff erent load capacity requirements.

Integrated Optimization Design of Carbon Fiber Composite Framework for Small Lightweight Space Camera

Shuai Yang,Wei Sha,Changzheng Chen,Xingxiang Zhang,Jianyue Ren 한국광학회 2016 Current Optics and Photonics Vol.20 No.3

A Carbon Fiber Composite (CFC) framework was designed for a small lightweight space camera. According to the distribution characteristics of each optical element in the optical system, CFC (M40J)was chosen to accomplish the design of the framework. TC4 embedded parts were used to solve the lowaccuracy of the CFC framework interface problem. An integrated optimization method and the optimizationstrategy which combined a genetic global optimization algorithm with a downhill simplex local optimizationalgorithm were adopted to optimize the structure parameters of the framework. After optimization, thetotal weight of the CFC framework and the TC4 embedded parts is 15.6 kg, accounting for only 18.4%that of the camera. The first order frequency of the camera reaches 104.8 Hz. Finally, a mechanicalenvironment test was performed, and the result demonstrates that the first order frequency of the camerais 102 Hz, which is consistent with the simulation result. It further verifies the rationality and correctnessof the optimization result. The integrated optimization method mentioned in this paper can be applied tothe structure design of other space cameras, which can greatly improve the structure design efficiency.

On the conjecture O of GGI for <i>G</i>/<i>P</i>

Cheong, Daewoong,Li, Changzheng Elsevier 2017 Advances in mathematics Vol.306 No.-

<P><B>Abstract</B></P> <P>In this paper, we show that general homogeneous manifolds G / P satisfy Conjecture O of Galkin, Golyshev and Iritani which ‘underlies’ Gamma conjectures I and II of them. Our main tools are the quantum Chevalley formula for G / P and a theory on nonnegative matrices including Perron–Frobenius theorem.</P>

Integrated Modeling for the Design of Deformable Mirrors Using a Parametric Module Method

Junqing Zhu,Wei Sha,Changzheng Chen,Xingxiang Zhang,Jianyue Ren 한국광학회 2015 Current Optics and Photonics Vol.19 No.5

Active optics is a key technology for future large-aperture space telescopes. In the design of deformablemirrors for space applications, the design parameter trade-off between the number of regularly configuredactuators and the correction capability is essential but rarely analyzed, due to the lack of design legacy. This paper presents a parametric module method for integrated modeling of deformable mirrors withregularly configured actuators. A full design parameter space is explored to evaluate the correctioncapability and the mass of deformable mirrors, using an autoconstructed finite-element parametric modelingmethod that utilizes manual finite-element meshing for complex structures. These results are used to providedesign guidelines for deformable mirrors. The integrated modeling method presented here can be used forfuture applied optics projects